1. Field of the Invention
The present invention relates to a tubular electronic circuit housing of the type employed for submarine telephone transmission-link repeaters.
This type of housing is intended to reconcile different requirements which include high mechanical strength for withstanding cable laying and recovery operations while at the same time affording resistance to the sea-bottom pressure, high electrical insulation of circuits which may be at a very different electric potential with respect to the sea ground potential by reason of their mode of remote power supply from the ends of the cable link, and efficient removal of heat from the electronic circuits t the external medium.
In the case of present-day transmission systems which operate at very high speed, the electronic circuits dissipate a larger amount of heat. Should it be found desirable to guard against any danger of a considerable increase in operating temperature since this adversely affects the reliability of these circuits in the long term, it is accordingly necessary to increase the heat-dissipating capacity of the circuit housing.
2. Description of the Prior Art
With a view to solving the problem outlined in the foregoing, a number of different design solutions have already been provided in the prior art.
One known solution described in French Pat. No. FR-A-2 558 664 consists of a repeater housing in which the electronic circuits are arranged in the form of function-specialized or dedicated modules enclosed in cases having the shape of thick disks and stacked within a tubular shell of pressure-resistant steel. Each module has a central partition for supporting electronic circuits, said partition being surrounded by an annular casing equipped on four sides with resilient shoes which are applied on the internal wall of the tubular shell and have the double function of providing electrical insulation and transmitting heat to the shell. Apart from the complexity of construction of the shoes, this structure has the disadvantage of imposing a flow path of substantial length including throttled portions through which the heat flow has to pass before it can be removed through the outer shell.
In another known repeater housing disclosed in U.S. Pat. No. 4,528,615, the electronic circuits are disposed in modules mounted within frames in the form of cylindrical sectors or so-called segments assembled in a group of three each extending through an angle of 120.degree. and forming a single cylindrical unit, this unit being placed within a tubular jacket which is designed to withstand pressure and to provide electrical insulation. The internal diameter of the tubular jacket is slightly larger than that of the cylinder formed by the assembled frames in order to make allowance for deformations which are liable to occur as a result of the external pressure. The frames are applied against the internal wall of the jacket by means of intercalary springs which tend to move said frames away from each other. The disadvantage of this structure lies in the fact that, in order to remove heat by conduction through the tubular jacket, it is necessary to establish an intimate contact between accurately curved surfaces which must ensure a perfect fit. However, one of these surfaces is liable to undergo deformation under the action of the external pressure and the mounting system which involves the use of intercalary springs may not be capable of uniform gap-width distribution and would thus be liable to produce misalignments.